Machine for sharpening cutting tools

ABSTRACT

A machine for sharpening cutting tools by means of a grinding wheel, particularly cutting bits of mining machinery, comprises a series of units mounted on a general bed and grouped by a common system of electro- and hydraulic drives, each unit including a support with a clamping device for holding and rotating the workpiece when sharpening, and a spindle head having a sleeve with a drive and a spindle with a grinding wheel. The spindle is mounted in the sleeve and an elastic link connects the sleeve to the body of the machine such that the force from the grinding wheel interacting with the workpiece is opposed and controlled by this link. When dressing the grinding wheel, the elastic link is locked by a power cylinder.

United States Patent [72] Inventors 54] MACHINE FOR SHARPENING CUTTING TOOLS 2 Claims, 4 Drawing Figs.

[52] U.S.Cl 51/119, 51/124 [51] 1nt.C1 B241) 7/00 [50] Field ol'Search 51/119, 120, 124

[56] References C i ted UNITED STATES PATENTS 2,655,769 10/1953 Lewis 51/119 X 3,114,988 12/1963 Garrison 51/124X FOREIGN PATENTS 912,057 5/1954 Germany 51/124 Primary Examiner- Harold D. Whitehead A!!0rne \--Waters, Roditi, Schwartz & Nissen ABSTRACT: A machine for sharpening cutting tools by means of a grinding wheel, particularly cutting bits of mining machinery, comprises a series of units mounted on a general bed and grouped by a common system of electroand hydraulic drives, each unit including a support with a clamping device for holding and rotating the workpiece when sharpening, and aspindle head having a sleeve with a drive and a spindle with a grinding wheel. The spindle is mounted in the sleeve and an elastic link connects the sleeve to the body of the machine such that the force from the grinding wheel interacting with the workpiece is opposed and controlled by this link. When dressing the grinding wheel, the elastic link is locked by a power cylinder.

PATENTEU JUN29 I97! SHEET 1 OF 2 IlESf-iUJJYES PATENTEU JUN29 I911 SHEET 2 BF 2 MACHINE FOR SHARPENTNG CUTTING TOOLS The present invention relates to cutting tool by sharpeners using an abrasive wheel and has particular reference to the sharpening of cutting bits of mining machinery such as coal cutting and loading machines.

Abrasive cutting tool sharpening is known to be favored as compared to other sharpening methods, including diamond and electrochemical ones, due to the fact that abrasive sharpening features maximum efficiency at minumum costs of tool wear, as well as tool surface finish suitable for mining machinery tools.

A peculiarity of abrasive sharpening ofa hard alloy metal is that the hardness value of abrasive grains is comparatively to that of the hard alloy involved, as well as in that instantaneous high temperatures (up to 2000 C.) arise within the contact zone.

lnasmuch as abrasive grains are arranged or oriented in a wheel at random and they differ considerably from one another by their cutting ability, the heat distribution in the surface layer of the tool being sharpened differs from that in the under layers thereof which gives rise to high thermal stresses, especially when being cooled down. For instance, in a hard alloy with the elastic modulus E=l0 kg per sq.cm. and the linear expansion coefficient a=6. heating by 100C. is liable to cause stresses 6=30 kg per sq.mm.

These stresses along with strains arising from mechanical interaction of the cutting grains and hard alloy involved, cause the appearance of burnt spots and microcracks in the latter which to a considerable extent effect adversely the working capacity of the tool being sharpened. The same stresses while acting upon the abrasive wheel result either in attrition and fusion of grains and, consequently, in the loss of the cutting ability thereby, or in a fast chipping out of the whole grains and therefore in a complete or disastrous" wearout of the wheel, or, else, in splintering, pointing and replacing of the cutting grains thereof.

In an attempt to eliminate the aforementioned undesirable effects, the method of the so-called elastic sharpening has been made use of which consists in incorporating an elastic member into the system machine-abrasive wheel--tool being machined." In accordance with different data obtained, the method in question is capable of increasing the efficiency of machining by ID to 30 times, reducing the specific consumption of abrasives by 5 to 10 times, and it ensures higher surface finish and absence of cracks in the hard alloy involved.

Increased efficiency and higher quality of machining are attained by virtue ofoperatively controlling the pressure exerted by the tool being sharpened on the abrasive wheel irrespective of the amount of metal removed and the degree of wear of the wheel. Furthermore, provision of the elastic member makes it possible to set an optimum and preselected pressure force directly, through the intermediary of the rate of feed, and to keep said. force practically constant.

A machine of such a type has been described, in particular, in Polish Pat. No. 36,510. The tool sharpener disclosed therein features a spring-loaded carriage provided with a clamping fixture for gripping the tool to be sharpened, and a grinding wheel made fast on the spindle. Yet in this case the springloaded carriage fails to provide the required axial sensitivity with a high rigidity in directions perpendicular to the longitudinal axis thereof.

This is accounted for by the fact that the clamping fixture used for fastening the tool being sharpened, features large overhang with respect to the carriage supports which necessitates the use of rolling contact guides to avoid possible jamming; this, of course, adversely affects constructional rigidity of the carriage. The jamming moment will rise still more if the carriage guides are brought out of the zone of sharpening with a view to prevent them from rapid wearout.

It is an object of the present invention to provide a cutting tool sharpener, that incorporates a more sensitive elastic member regulating the force of interaction between the wheel and the tool being sharpened, said member at the same time featuring high rigidity in all directions other than axial.

According to the present invention, disclosed hereinbelow is a sharpener for cutting tools, mostly cutting bits of mining machinery. The sharpener has a grinding wheel made fast on the spindle, as well as a carriage with a clamping fixture to hold the tool being sharpened. To control the force of interaction between the grinding wheel and the tool being sharpened provision is made therein for an elastic link or member. According to the invention, the spindle is mounted in a rotatable sleeve to which the elastic member made fast on the machine housing is coupled.

It is due to the interconnection between the sleeve and the elastic member that but light pressure is exerted upon the abrasive grains of the grinding wheel, whereby the possibility of the grains chipping out is reduced.

Under ideal conditions, that is when the pressure upon the grains is not in excess of the ultimate strength thereof, the wear of the grains is extremely low being in effect due to adhesion and diffusion; however, even under these conditions the grains will lose their cutting ability after a certain period of time and therefore will need replacement.

The pressure exerted upon the grinding wheel is too low for the used-up grains to be chipped out which is necessary to restore the wheel cutting ability; that is why the wheel should be dressed or trimmed after the sharpening of each cutting tool.

To hold the sleeve against axial displacement during the wheel dressing procedure, said sleeve is connected to a power cylinder.

An advantageous feature of the present invention consists, first and foremost, in that it makes possible more accurate adjustment of the loads imparted by the grinding wheel to the tool being machined in a strictly axial direction, with the provision of a considerable rigidity in directions normal to the axis thereof.

The invention will become apparent from the following description of an exemplary embodiment thereof, reference being made to the following drawings, wherein:

PEG. 1 is a schematic diagram of the machine disclosed in the present invention, complete with an abrasive grinding wheel dressing attachment and tool feed chutes;

FIG. 2 is a view taken along the arrow A;

FIG. 3 is a section taken on the line BB of FlG. 1; and

FIG. 4 is a perspective view of the clamping fixture of the machine with a tool in the process of sharpening with an abrasive wheel.

Now referring to FIG. 1, a spindle 1 carrying an abrasive grinding wheel 2 runs in bearings 3 which are eccentrically mounted in a sleeve 4, said sleeve being located in a housing 5 of the machine and having a holder 6 with which an elastic link 8 interacts through the intermediary of rollers 7, said link being connected to the machine housing 5.

The spindle 1 is driven in rotation from a motor 9 via a V- belt drive 10 and performs planetary motion due to rotation of the sleeve 4 from the same motor 9 through a V-belt drive 11 and a gearing 12. To eliminate the slack in the V-belt drive 10 due to planetary motion of the spindle 1, a belt tensioning roller 13 is provided.

Guides 14 are provided on the housing 5 along which rods 16 of a carriage 17 are imparted translational motion from a power cylinder 15. The carriage 17 has a hollow space 18, wherein a piston 19 is accommodated which performs a reciprocal motion under the effect of a fluid medium supplied into said space. The piston 19 is connected to a clamping fixture 20 which holds in place the tool being sharpened, for example a cutter bit, as well as turns it in the course of sharpenmg.

FIG. 4 illustrates the clamping fixture 20 in detail. Said fix ture has a fixed jaw 21 connected to the piston 19 and ajaw 23 made movable by means of a power cylinder 22 and capable of forcing a cutter bit 24 being sharpened against the jaw 21.

-Provision is made in the herein proposed machine for chutes 25 and 26 (FIGS. 1 and 2) to feed the cutter bits to be sharpened and to receive those already sharpened. The chute 25 is disposed parallel to the direction of travel of the carriage 17, whereas the chute 26 is arranged normal to the chute 25 and above its sloping bottom 27. Made fast on the chute 25 opposite to the discharge end of the chute 26 is a springloaded swiveling element 28 provided with a curvilinear recess 29 for centering the cutter bit 24 being sharpened, as well as with a projection 30 in the bottom portion thereof upon which the cutter bit 24' rests with one of its ends, whereas the other end of said bit rests upon the end of the chute 26.

When the carriage 17 travels along the grinding wheel 2 the cutter bit 24' is engaged in between the jaws 2i and 23 of the clamping fixture 20. The gripping of the bit by said jaws is effected as a result of a command from a slide valve 31 which is actuated by one of the rods 16 of the carriage 17 via a ratchet lever 32. The chute 25 also carries a spring-loaded stop 33 which knocks out a sharpened bit from the clamping fixture upon releasing the pressure inside the cylinder 22.

As it has been stated hereinbefore, the machine disclosed herein makes provision for periodical dressing of the grinding wheel 2. An attachment used for the purpose has progressively moving rack 34 (FIGS. 1 and 3) which is in mesh with a toothed quadrant 35, wherein a ratchet gear is mounted. A ratchet wheel 36 of that mechanism is connected to a motion screw 37 carrying a nut 38, whereon a wheel dressing tool 39 is mounted. The grinding wheel 2 having been used up completely, the wheel dressing tool is returned to the initial position by means of a handwheel 40 associated with the motion screw 37. To keep the sleeve 4 against axial displacement while dressing the wheel 2, provision is made for a cylinder 41 located on the housing 5, said cylinder resting with its movable portion upon the holder 6 of the sleeve 4 via a roller 42, said holder being fixed in place on the opposite side by means of a roller 43.

It is evident that the attachment for dressing the wheel 2, the clamping fixture 20 and feed chutes and 26 described hereinabove may have an alternative engineering construction and will be successfully used in the present invention.

Given below is a description of the operating principle of the machine disclosed herein.

The carriage 17 with the cutter bit 24 gripped therein approaches the abrasive grinding wheel 2 so as to press against the latter; as a result the wheel 2 together with the sleeve 4 is made to travel over a certain distance, the roller 7 acts upon a transmitter 45 via a pusher 44, whereupon said transmitter delivers a signal to disengage the feed motion of the carriage l7. Provision of the elastic member 8 enables the bit to be pressed against the wheel 2 with a constant force irrespective of the degree of wear of the latter. Once the tool being sharpened has made a predetermined number of turns, the piston 19 retracts the carriage 17 from the wheel 2 and the clamping fixture 20 releases the bit. Further backward motion of the carriage l7 results in the bit meeting the stop 33 to be knocked out thereby from the clamping fixture 20 into the chute 25. Thereupon the carriage 17 approaches the chute 26, receives a fresh bit to be sharpened, then returns to the grinding wheel 2 and the entire working process is repeated. Dressing of the wheel 2 is carried out during the retraction of the carriage 17.

When grinding the cutting edges of the cutter bit, the latter is free to rotate together with the clamping fixture 20 with respect to the grinding wheel, as has been stated hereinabove.

The invention is not to be limited to the specific and preferred embodiment thereof disclosed herein by way of example and may have modifications not departing from the scope of the following claims.

We claim:

1. A machine for sharpening cutting tools, particularly cutting bits of mining machinery, said machine comprising: a spindle; a grinding wheel fastened on said spindle; a housing for said machine; a sleeve in which said spindle is mounted, said sleeve being located in said housing; means for imparting rotation to said sleeve; a displaceable carriage including a clamping fixture in which a tool being sharpened is gripped and can be applied against said grinding wheel; elastic link means connected to said housing and to said sleeve and extending parallel to said spindle to oppose the pressure of the tool against the grinding wheel and provide a present force of interaction between said grinding wheel and said tool; a piston and power cylinder connected to the sleeve to lock the elastic link means against axial displacement during dressing of the grinding wheel.

2. A machine as claimed in claim 1 comprising means for displacing the carriage towards and away from the grinding wheel along an axis parallel to said spindle. 

1. A machine for sharpening cutting tools, particularly cutting bits of mining machinery, said machine comprising: a spindle; a grinding wheel fastened on said spindle; a housing for said machine; a sleeve in which said spindle is mounted, said sleeve being located in said housing; means for imparting rotation to said sleeve; a displaceable carriage including a clamping fixture in which a tool being sharpened is gripped and can be applied against said grinding wheel; elastic link means connected to said housing and to said sleeve and extending parallel to said spindle to oppose the pressure of the tool against the grinding wheel and provide a present force of interaction between said grinding wheel and said tool; a piston and power cylinder connected to the sleeve to lock the elastic link means against axial displacement during dressing of the grinding wheel.
 2. A machine as claimed in claim 1 comprising means for displacing the carriage towards and away from the grinding wheel along an axis parallel to said spindle. 